• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.2
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• pp.67-74
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• 2017

In this work, the effects of nano $TiO_2$ on functionality and stability of low density polyethylene (LDPE) composite films were investigated for food packaging application. LDPE-nano $TiO_2$ composite films were prepared with various $TiO_2$ contents (0, 0.5, 1.0, 3.0 and 5.0wt%) by melt-extrusion and their basic properties such as crystallinity, chemical bonds and surface morphology were examined by XRD, FTIR and SEM. Ultraviolet (UV) light barrier property of as-prepared LDPE-nano $TiO_2$ composite films was also studied and the presence of nano $TiO_2$ resulted in significant improvement of UV light barrier compared to the pure LDPE film. To evaluate influence of nano $TiO_2$ on LDPE properties required as packaging material, thermal, mechanical, gas barrier and optical properties of LDPE-nano $TiO_2$ composite films were characterized with various analytical techniques including TGA, UTM, OTR, WVTR and UV-vis spectroscopy. As a result, except optical property of LDPE, no significant effects were found in other properties. Opacity of pure LDPE was greatly increased with increasing concentration of nano $TiO_2$.

• Food Science and Preservation
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• v.4 no.3
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• pp.251-258
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• 1997

The quality changes of strawberries packaged using low density polyethylene (LDPE) film filled with 3% silver-coated ceramic (WC30) and filled with it and 0.1% chitin (CWC) were investigated during storage at 2$0^{\circ}C$ for 5 days. In gas composition within film bag, CWC and WC30 kept higher CO2 concentration than LDPE without silver-coated ceramic and chitin (CO) did during 5 day storage. The weight loss of strawberries during storage was the smallest in WC30 and the largest in CWC in 5 days. Hardness of strawberries was the highest in WC30 and the lowest in CO during 5 day storage. pH of strwberries was increased a little until 1 day and was not changed after 1 day storage, and soluble solid content was not changed during storage. Vitamin C content was decreased significantly until 2 day storage and decreased a little after 2 days. There is no differences in the change of vitamin C content among the packaging materials. In color measurement, lightness was the highest in WC 30 and in sensory evaluation, all characteristics also had the highest scores in WC30. In conclusion, better quality of straberries was shown in WC30 than in CWC and CO during storage.

• Elastomers and Composites
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• v.15 no.1
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• pp.3-9
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• 1980

The oxygen permeability and it's proofness of te various commercial polymer films have been investigated at the constant pressure and temperature. Oxygen proofness, the reciprocals of the oxygen permeability for the various samples, were determined by means of a coulometric oxygen permeability tester. The testing of sample films was performed at constant temperature $(23{\pm}1^{\circ}C)$ under 1 atm. for 24 hours. The order of the relative proofness observed are as follows; oriented Nylon (O. Nylon)> oriented Polyester (O. PET)>nonoriented Nylon (N. Nylon)>nonoriented Polyester (N.PET)> rigid Polyvinyl chloride (Rigid PVC)>semirigid Polyvinyl chloride (Semirigid PVC)> oriented Polypropylene (O. PP)>plasticized Polyvinyl chloride (P. PVC)> casted Polypropylene (C. PP)> low density Polyethylene (LDPE)>high density Polyethylene (HDPE, Inflation)> high density-polyethylene (HDPE, T-die) The oxygen proofness of the films was increased with the polarity cf polymer, the film thickness and mechanical orientation and decreased with the addition of plasticizer in PVC. For the use of wrapping materials, one film with the polar property in the main chain of the polymer molecule and the others with nonpolar property in it are laminated for the protection from oxygen and moisture.

• Food Science and Preservation
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• v.16 no.5
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• pp.605-611
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• 2009

Korean Baechu cabbage(known as Chinese cabbage) brined in 0%, 5% and 10% (all w/v) salt solutions were packed using high-density polyethylene film (HDPE-film), low-density polyethylene film (LDPE-film), or Mirafresh film (MF-film, US patent No. 5972815), and stored at 4C for 4 weeks. Changes in pH and salinity, and microorganism counts (lactic acid bacteria and total bacteria), were investigated. There was no significant difference in the pH change in cabbage stored using various films when the vegetables were not salted. However, the pH was most stable in Baechu cabbage prepared using 10% salt solution. Cabbage treated with 0%, 5%, and 10% salt showed salinity values of 0.83%, 1.17% and 1.62%(all w/w), respectively, after 4 weeks of storage by LDPE-film. When cabbage was treated with the highest concentration of salt solution, the count of lactic acid bacteria increased but that of total bacteria decreased. The pH from pH 6.10 to pH 4.32, pH 5.68, and pH 5.92 in brined cabbage packed in HDPE-film, LDPE-film, and MF-film, respectively, after 4 weeks. When MF-film was used, the pH showed the greatest stability of all films tested, regardless of the concentration of salt solution employed in brining. The counts of lactic acid bacteria and total bacteria increased by all tested films during storage. Cabbage packed by MF-film showed the lowest increase in bacterial counts. In conclusion, MF-film was found to be the most effective packaging material for Baechu cabbage and brining in 10% salt solution was optimal to enhance the shelf life of the vegetable. LDPE-film was more effective than was HDPE-film for storage of brined cabbage.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.162.2-162
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• 2001

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.52-60
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• 2005

In this study, low density polyethylene/organo-clay nanocomposites were prepared by melt blending. Thermal property, structure, and morphology of the LDPE/organo-clay nanocomposites were investigated. When the composition ratios of the compounds of LDPE/PE-g-MA/organo-clay were 90/10/1~10 (w/w/w), X-ray diffractograms of LDPE/organo-clay nanocomposites revealed that the intercalation of polymer chains lead to increase the spacing between clay layers. TEM microphotographs showed that LDPE was intercalated into organo-clay. TGA performed under air atmosphere demonstrated a great increase in thermal stability of the LDPE/organo-clay nanocomposties. The maximum decomposition temperature of LDPE/organo-clay nanocomposite was increased about $80^{\circ}C$ compared with pure LDPE. When the organo-clay contents were 1.0~5.0 wt%, the LOI values were increased with increasing the organo-clay content, but in the case of the contents more than 5.0 wt%, the LOI values were not increased any more.

• Food Science and Preservation
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• v.1 no.2
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• pp.93-98
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• 1994

Fresh ginseng was packed by using available commercial plastic films of polyvinyl chloride (PVC), cast polypropylene (CPP) and low density polyethylene (LDPE). PVC was used as a wrapping on polystyrene tray, and CPP and LDPE were applied as pouch packages. Gas composition of the package and keeping quality of ginseng in the packages were evaluated for 20 day storage at 5$^{\circ}C$. LDPE (27$\mu\textrm{m}$ thick) Package modified the Package atmosphere to 11.7% O2 and 2.1% CO2, gave low microbial growth and good sensory score after 20 day storage.

• Korea-Australia Rheology Journal
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• v.16 no.3
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• pp.147-152
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• 2004

Ultrasound-assisted melt mixing was applied to blending polystyrene (PS) and low density polyethylene(LDPE). The influence of the ultrasonic irradiation on the morphology and mechanical properties of the blends was investigated. It was observed that the domain sizes of the blend were significantly reduced and phase stability was well sustained even after a thermal treatment. Such morphological feature was consistent with the improvements in mechanical performance of the blends. The desirable results of ultrasonic compatibilization are mainly attributed to the in-situ formation of PS-LDPE copolymers as confirmed by a proper separation experiment. An important relationship between ultrasonic irradiation time and mechanical properties is revealed and an issue on the thermal stability of the blend is discussed.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.81-86
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• 2005

This study has investigated radiation degradation of low density polyethylene(LDPE). Samples were irradiated up to 800kGy using a $Co^{60}\;\gamma-ray$ at a dose rate of 5kGy/hr in the presence of air atmosphere at room temperature. After irradiation, storing for 2 weeks, free radical measurement of LDPE has established by electron spin resonance(ESR). ESR measurement showed that free radical concentration(FRC) was increased with radiation dose and decreased with the time. The radical types showed alkyl, allyl, and peroxy radical with the irradiation, these changed to peroxy radical with the time.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.1
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• pp.42-49
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• 1992

Charge accumulation characteristics in low density polyethylene (LDPE) has been discussed based upon the internal charge distrubution measured by the pulsed electroacoustic technique. When the negative voltage with respect to earth is applied to the upper electrode, the negative charges near the anode and the positive charges near the cathode are accumulated in LDPE. Also, there was an asymmetric behavior of charge accumulation exhibiting that the charge accumulation near the anode keeps increasing whereas that near the cathode increases first and then decreases. Besides, under the present test conditions the internal charge distrubution becomes stabilized eventually. When the positive voltage with respect to earth is applied to the upper electrode, on the other hand, no such asymmetric charge accumulation was found. Therefore, it can be concluded that the heterocharges are accumulated at the surface region of LDPE subjected to high do voltages and that the begavior of charge accumulation depends on the polarity of do voltage and the position of charge accumulation.